kernel panic when unmount removed usbdrive

hi, i've got 2 kernel panics.. when tried to unmount already
removed an
usbdrive
actually i have reported this  problem, but  after some
google  found that
this is not new :(

this problem is known at least for 1 year.. this is bad.

anybody knows any work-around ?

thank u in advance

ps:
FreeBSD some.domain 7.0-RELEASE FreeBSD 7.0-RELEASE #0: Sun
Feb 24 19:59:52
UTC 2008 rootlogan.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC
i386
_______________________________________________
freebsd-usbfreebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-usb
To unsubscribe, send any mail to
"freebsd-usb-unsubscribefreebsd.org"

On Thu, 28 Feb 2008 09:27:51 -0600
Octavian Covalschi <octavian.covalschigmail.com> wrote:

> hi, i've got 2 kernel panics.. when tried to unmount
already removed
> an usbdrive
> actually i have reported this  problem, but  after some
google  found
> that this is not new :(
> 
> this problem is known at least for 1 year.. this is
bad.

This problem has been known for a lot longer time.
However, "most people" only complain about it -
and they also think it
is easy to fix this problem.

Well, it is not easy - in fact it is very hard to fix this
problem. For
data on this, please search the mailing list archives of
FreeBSD.

> anybody knows any work-around ?

Yes - the work around is this: don't do that!
Do _not_ remove any mass storage device before unmounting
it.

If you can't learn to live with this workaround, please do
not use
removable mass storage devices with FreeBSD.

HTH
-- 
Regards,
Torfinn Ingolfsen

_______________________________________________
freebsd-usbfreebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-usb
To unsubscribe, send any mail to
"freebsd-usb-unsubscribefreebsd.org"

In message:
<20080228170826.1fa1cadd.torfinn.ingolfsenbroadpark.no>
            Torfinn Ingolfsen <torfinn.ingolfsenbroadpark.no> writes:
: > anybody knows any work-around ?
: 
: Yes - the work around is this: don't do that!
: Do _not_ remove any mass storage device before unmounting
it.

run current and you have better results.

The problem is that error propagation inside of the buffer
cache code
and file system code doesn't handle ENXIO very well.  It
takes time to
work through it.

One could, in theory, use QEMU to make it easier to test. 
Alas, I've
not had time to work through the setup.

Warner


_______________________________________________
freebsd-usbfreebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-usb
To unsubscribe, send any mail to
"freebsd-usb-unsubscribefreebsd.org"

I think I've already made my point regarding this bug, but
since I stay
on this mailing list primarily to see the fix through to
completion, it
would be silly not to comment when everyone else seems to do
that 

On Thu, 2008-02-28 at 09:27 -0600, Octavian Covalschi
wrote:
> this problem is known at least for 1 year.. this is
bad.

The problem was known over five years ago (usb/46176). I
offered a first
working patch set for private review in September 2004, but
never took
the time to follow up. With hindsight, that was a mistake.
You see, the
thing is that the panic-at-usb-drive-removal bug has been
with us for so
long that most long-term FreeBSD users have gotten used to
it. They know
that the drive must be unmounted before the USB stick can be
pulled out,
and they have probably forgotten the horror experienced when
they first
made the pull-out-first mistake themselves. That is why you
get advice
like "don't do that", although a bug fix is a very
reasonable request.

> anybody knows any work-around ?

Right now, your best bet is to take Warner's advice and try
8.0-CURRENT,
since none of the known patches have been merged to the 7.0
track yet.
However, I honestly don't know how he can get anything
stable without
the final scsi_da.c patch, since I had something like 100%
reproducible
crashes when I updated my system from late 7.0 to early 8.0.
You might
want to apply patches from http://www.gulbra.
net/freebsd-usb/ yourself,
but keep in mind that CURRENT is a moving target, so I can't
guarantee
that the patches are still working perfectly. Also, please
remember to
use -o sync when mounting the drive. The other case is less
tested...

> thank u in advance

You're welcome! And if you're uncomfortable with applying
weird patches
and recompiling bleeding-edge kernels, please don't give up
hope! It's
hopefully just a matter of months before we have an
acceptable solution
in one of the official releases.

On Thu, 2008-02-28 at 17:08 +0100, Torfinn Ingolfsen wrote:
> This problem has been known for a lot longer time.
> However, "most people" only complain about it
- and they also think it
> is easy to fix this problem.
> 
> Well, it is not easy - in fact it is very hard to fix
this problem. For
> data on this, please search the mailing list archives
of FreeBSD.

You know, the good thing about thinking something is easy is
that you
get the nerve to actually start working on the problem. I
agree that it
is not a trivial fix. I pride myself on being able to fix
almost any bug
within a day. At least, that's what it says on my business
cards, but in
this case there were several underlying issues, so say one
week of deep
analysis and patching to reach the state where I couldn't
reproduce any
version of the problem. I'd call that "hard", not
"very hard" 

> Yes - the work around is this: don't do that!
> Do _not_ remove any mass storage device before
unmounting it.
> 
> If you can't learn to live with this workaround, please
do not use
> removable mass storage devices with FreeBSD.

There is a piece of potential wisdom that I've been toying
with lately:
You get the life you accept. Read that again and give it
some thought!
What you accept. Not the life you want, not even the life
you deserve,
but the life you accept, because that is where you will stop
striving
for something even better. In this case, I have no doubt
that the very
moment we decide that it is truly unacceptable for a FreeBSD
kernel to
panic in a common scenario like this, that is when we will
start to see
some really quick progress in this area.

/Henrik


_______________________________________________
freebsd-usbfreebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-usb
To unsubscribe, send any mail to
"freebsd-usb-unsubscribefreebsd.org"

In message: <1204240017.82302.119.camelParticle>
            Henrik Gulbrandsen <henrikgulbra.net> writes:
: Right now, your best bet is to take Warner's advice and
try 8.0-CURRENT,
: since none of the known patches have been merged to the
7.0 track yet.
: However, I honestly don't know how he can get anything
stable without
: the final scsi_da.c patch, since I had something like 100%
reproducible
: crashes when I updated my system from late 7.0 to early
8.0. You might
: want to apply patches from http://www.gulbra.
net/freebsd-usb/ yourself,
: but keep in mind that CURRENT is a moving target, so I
can't guarantee
: that the patches are still working perfectly. Also, please
remember to
: use -o sync when mounting the drive. The other case is
less tested...

Henrik,

I've not forgotten your patches, but I haven't had the time
to
integrate them into the system.  I hope to have them ready
by 8.0, and
if I'm lucky, in time to MFC for 7.1.  Many of them are
MFCable,
although some of the underlying issues they expose can only
be fixed
properly in head since they may require ABI changes.  The
changes
should really be done at the fs level, since the current
patches will
leak resources and potentially have other bad effects.

I'd also like to have something between full sync and async
when
mounting removable file systems.  You want synchronous
metadata, but
async data blocks for performance often times.  I'm still
exploring
what this means...

Finally, I'd like to thank you again publicly for taking the
time and
initiative to see through the difficulties of this problem
and to
persist in presenting your solution to the developers.  It
made me
lose my fear of the buffer cache code, which ultimately will
be a good
thing.

Warner
_______________________________________________
freebsd-usbfreebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-usb
To unsubscribe, send any mail to
"freebsd-usb-unsubscribefreebsd.org"

On Thu, 28 Feb 2008 11:02:03 -0600
Octavian Covalschi <octavian.covalschigmail.com> wrote:

> no, i don't think it is easy, if it was i think it
already been fixed

I did not imply that you were in the group "most
people". 

> it is not a hobby to remove storage before unmounting
it, it's just
> happened, i even did not think it could
> bring kernel panic.
> in this case is a usbdrive.. but what happens if i have
a usb hdd
> drive? it will be the same? having a laptop and a
portable
> hdd may bring in situation that i just remove it form
usb...

Yes, it will be the same. anay removable media (at least the
ones that
end up being mounted) will behave this way, AFAIK. I'm sure
someone
will correct me if I'm wrong.

> actually as far i know usb is intented to have hotswap
devices.
> anyway, i'm just a user, and hearing and advice:
"don't do that" it
> is VERY unprofessional

I agree.
However, this is the status quo right now, and has been for
at least 4
years. There is no orher workaround - we (FreeBSD users)
will have to
live with this until developers who can fix this can free up
enough
time to do so. Note: am not blaming any developers for the
sad state
we're in - after all, this is a volunteer project.

> i can understand that it can be difficult, i'm a
programmer too, but
> anyway just to sat don';t do that is not at least nice

> >
> > If you can't learn to live with this workaround,
please do not use
> > removable mass storage devices with FreeBSD.
> >
> 
> don't be so mean 

No mean-nesss was intended, just trying to tell you in very
clear terms
what the state of this problem is.
Yes, it is harsh, but we will have to live with it for now.
-- 
Regards,
Torfinn Ingolfsen

_______________________________________________
freebsd-usbfreebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-usb
To unsubscribe, send any mail to
"freebsd-usb-unsubscribefreebsd.org"

On Fri, 29 Feb 2008 00:06:57 +0100
Henrik Gulbrandsen <henrikgulbra.net> wrote:

> You know, the good thing about thinking something is
easy is that you
> get the nerve to actually start working on the problem.
I agree that
> it is not a trivial fix. I pride myself on being able
to fix almost
> any bug within a day. At least, that's what it says on
my business
> cards, but in this case there were several underlying
issues, so say
> one week of deep analysis and patching to reach the
state where I
> couldn't reproduce any version of the problem. I'd call
that "hard",
> not "very hard" 

My use of the phrase "very hard" here didn't
reflect only on the
technical issues of the problem, but all the issues:
1. there are a limited (very limited?) number of developers
with enough
insight to even try to fix this prtoblem
2. the problem has been around for so long that any
"new" or "fresh"
developers will also hear that this problem is hard to fix,
and thus
probably avoid it
3. seasoned FreeBSD users and developers know how to
workaround; and
thus the problem remains "out of sight"
4. the few people who could fix this problem doesn't have
enough free
time to meet and discuss how to best solve it

It is very good that you have done something with the
problem in spite
of all this. Keep up the good work!

> There is a piece of potential wisdom that I've been
toying with
> lately: You get the life you accept. Read that again
and give it some
> thought! What you accept. Not the life you want, not
even the life
> you deserve, but the life you accept, because that is
where you will
> stop striving for something even better. In this case,
I have no
> doubt that the very moment we decide that it is truly
unacceptable
> for a FreeBSD kernel to panic in a common scenario like
this, that is
> when we will start to see some really quick progress in
this area.

I agree - you get the life you accept.
In my case, FreeBSD is just a very small part of my life
(hey - it's
just an operating system for computers, and life is so much
more than
computers to me), which means that the time I am willing to
spend on
problems in FreeBSD has to be weighed against other
activites.

That said - FreeBSD _is_ my favorite operating system.
-- 
Regards,
Torfinn Ingolfsen

_______________________________________________
freebsd-usbfreebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-usb
To unsubscribe, send any mail to
"freebsd-usb-unsubscribefreebsd.org"